Isomers Flashcards
Isomers
Same molecular formula only
Constitutional (structural) isomers
Same molecular formula
diff connectivity
Stereoisomers
Same molecular formula
Same connectivity
Conformational isomers
same molecular formula
same connectivity
does not require bond breaking to interconvert
Configurational isomers
same molecular formula
same connectivity
requires bond breaking to interconvert
Diastereomers
same molecular formula
same connectivity
requires bond breaking to interconvert
superimposable
cis-trans
Enantiomers
same molecular formula
same connectivity
requires bond breaking to interconvert
nonsuperimposable
Anti staggered
Biggest groups 180° away
Least potential energy, most stable
Gauche
Biggest groups 60° away
Second least potential energy
Second most stable
Eclipsed
Biggest groups 120° away
Second most potential energy
Second least stable
Totally eclipsed
Biggest groups back to back
Most potential energy
Least stable
Most stable position for the bulkiest groups in cyclohexane conformation
Equatorial
Chair flip
Equatorial becomes axial and axial become equatorial
But the groups that were up (wedge) remain up and the groups that were down (dashed) remain down
Chirality
Mirror image cannot be superimposed
Lack an internal place of symmetry
4 diff groups on shared carbon
Specific rotation
[α] = (α obs)/ (c x l)
α = degrees
c = g/mL
l = dm
racemic mixture
when both (+) and (-) enantiomers are present in equal concentrations
No optical activity observed
How many possible stereoisomers
2^n
n = # of chiral centers
Meso compound
a molecule w chiral centers that has an internal plane of symmetry
no optical activity
Fischer projection
- horizontal lines: bonds project out, wedges
- vertical lines: bonds going into plane, dashes
